Hello,
Here is a small report in attachement, done with 2.6.11-rc4.
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* Hardware is nforce3 250GB, booting debian pure64 on pata (Maxtor 30Gb 6E030L0) drive. The goal is to mount data found on a sata disk (seagate 200Gb ST3200822AS). The pata drive holds / and lvm partition with /usr, /var /tmp and /home.
The ultimate goal is to switch all this to the sata drive, which already holds a (barely used) swap partition.
* Soon after boot the console displays:
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device removed
...
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device removed
nv_sata: Primary device added
nv_sata: Primary device added
and the sata disk seems to spin down at the same time.
This is currently on 2.6.11-rc4, although I got the same behaviour with 2.6.10 and 2.6.11-rc3. Removing power from the drive and pluging it again seems to make te drive work some time , until it spins down again...

Seems like the hotplug code is triggering. That signals to me there is
some connection problem. Maybe you have a bad cable, or maybe the cable
is just seated improperly in one of the two SATA plugs.

It's also possible your motherboard or drive SATA plug is faulty, but I
would replace the cable first.